The present invention relates to projection displays and particularly to combining an electronic and overhead display in a single unit.
For many years overhead projectors have been popular as a means of projecting prepared transparencies or free-hand transparencies that are drawn in real-time, on to a display screen for viewing by a group (one or more) of viewers. More recently electronic displays, which are connected to various electronic data sources, have been used to project images normally seen on a computer screen on to a larger display screen for viewing by a group of viewers. Today, it is often necessary to equip conference or meeting rooms with both an overhead projector and an electronic display projector in order to accommodate uninterrupted presentations. This tends to be both expensive and somewhat awkward in switching between the projectors.
FIGS. 1a and 1b are diagrams showing a [top and] side view and a top view, respectively, for a typical overhead projector used in such applications. These projectors are typically packaged in two parts; e.g., a main projector housing 10 and a remote projection head 11. The main housing 10 consists of a bright, white light source 100 (lamp) along with its power supply (not shown), a rather large turning mirror 101, and a Fresnel lens 102 located just below a top glass media surface 103. The projection head 11 consists of a condensing lens 110, a smaller turning mirror 111, and a projection lens 112.
In operation, the operator (presenter) places a transparency on top of the glass media surface 103 just above the Fresnel lens 102. Light from the light source 100 is reflected and bent upward through the Fresnel lens 102, through the glass cover 103 supporting the transparency, and into the projection head 11. The light is modulated by a pattern on the transparency to provide an image with the dark areas of the transparency being black and the open areas of the transparency being white. In the projection head 11, the image is focused on to a smaller turning mirror 111 by means of a condensing lens 110. Light is then reflected off the turning mirror 111, through a projection lens 112, and on to an appropriate display screen 12, usually a white surface. The small turning mirror 111 can be tilted up and down to properly position the image on the screen and the projection lens 112 can be manually adjusted to properly focus the image on the screen. In the top view, the relative sizes of the projector""s large turning mirror 101, the transparency 102, and the projection head""s smaller turning mirror 111 are shown.
Electronic projectors have become quite popular in recent years due to their small size, lightweight, and high performance. These projectors are electronically driven with media content that is used to modulate the light and present either a color or black-and-white image on the display screen. The projectors come in different configurations, but usually use a spatial light modulator (SLM), such as a reflective digital micromirror device (DMD(trademark)) or liquid crystal device (LCD), to modulate the data. The projectors can be very small and lightweight, built around a single SLM and present a high-resolution, bright image with brilliant color representation. Electronic displays having two or three SLMs are also used for applications that require brighter projectors, such as for use in large conference halls.
FIG. 2 is block diagram for one configuration of a single-SLM electronic display projector. In this example, the projector is comprised of a white light source 200, which consists of a lamp and collector for gathering the light from the lamp and focusing it to a small spot at a point along the generated light beam. A rotating color filter wheel 201 is inserted at the focused spot of light in the light beam. A motor turns the wheel in synchronization with the electronic data being presented. The color wheel 201 is made up of red, green, and blue (primary colors) segments and transforms the clear light into sequential red, blue, and green light beams. In some cases, an optional white segment is added to the color wheel to help boost the overall brightness of the projector. In this configuration, light from the color wheel 201 is then passed through a light-integrating rod 202, through a condensing lens 203, and into a total internal reflective (TIR) prism 204. Inside this TIR prism, the light is reflected and directed on to the surface of a SLM 205 where it is modulated according to the electronic data content. Modulated light is then reflected off the surface of the SLM 205, back through the TIR prism 204, through a projection lens 206, and on to a display screen 207. Other optical configurations for such projectors do not necessarily utilize a TIR prism and/or integrating rod.
Together, these two projector types satisfy most presentation needs. However, what is needed is a flexible projection system that offers both of these projection capabilities in a single, reasonably priced package. The projector embodiments of the present invention meet this need by providing a single high-performance, comprehensive solution that addresses both the overhead projection display needs, as well as electronic display needs. The invention further provides a new function of capturing drawn transparencies from the overhead function and integrating (overlaying) these with the electronic content in terms of both an optical projected image and stored data.
The present invention discloses three embodiments of a combined overhead projector and electronic display projector system. The combined projector of this invention serves three major purposes. First, the overhead projector serves to display transparencies. Second, the electronic display device projects electronic data from several different types of electronic input sources, including NTSC and HDTV television, VGA (computer), S-video, etc. Third, both the overhead functionality and electronic display functionality can be used simultaneously to combine the data from both projectors. For example, while an electronic image is being displayed, the user can simultaneously draw in real-time a transparency so both images are superimposed on the display screen. In this mode, a camera mounted to the remote overhead projection head can be used to capture the drawn or superimposed image. Once captured by the camera, the new superimposed image can be electronically stored for future use.
Historically, overhead projectors and electronic projection displays have required the purchase of two completely separate products to address the two applications. In addition, before this invention it was difficult to simultaneously provide the functions of both the overhead projector display and the electronic projection display.
This invention provides a single comprehensive solution, which addresses both the overhead projection display needs as well as electronic projection display needs. The invention further provides a new function of integrating both drawn transparencies and electronic content in terms of both an optical projected display and electronic stored data.